Returns the configured JSON encoding library for Phoenix.

To customize the JSON library, including the following in your config/config.exs:

config :phoenix, :json_library, AlternativeJsonLibrary

The configured module is required to provide three functions:

• decode!/1 — decodes a JSON binary, raising on invalid input
• encode!/1 — encodes a term to a JSON binary, raising on encoding errors
• encode_to_iodata!/1 — encodes a term to JSON as iodata, raising on encoding errors.

These correspond to the single-argument, raising variants of the functions provided by Elixir's built-in JSON module. A conforming :json_library module does not need to implement any other functions JSON has, that are not defined above.

Returns the :plug_init_mode that controls when plugs are initialized.

We recommend to set it to :runtime in development for compilation time improvements. It must be :compile in production (the default).

This option is passed as the :init_mode to Plug.Builder.compile/3.